badsig error on update from private ppa due to 0-byte Release file

Reported by Martin Pool on 2011-08-29
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Launchpad itself
High
Unassigned

Bug Description

I'm running apt-get update on a machine with access to the canonical-ux/walled-garden ppa. It has always worked here in the past, but now it fails with

W: GPG error: https://private-ppa.launchpad.net oneiric Release: The following signatures were invalid: BADSIG 6D8F9D432E787113 Launchpad Private PPA for Canonical UX Team

This might be related to bug 807303 or bug 485151.

In /var/lib/apt/lists I see

-rw-r--r-- 1 root root 0 2011-08-29 09:03 private-ppa.launchpad.net_canonical-ux_walled-garden_ubuntu_dists_oneiric_Release

and updating again does not update that file.

Analysis
========

archivepublisher writes files non-atomically, possibly combined with custom apache validator settings.

Martin Pool (mbp) wrote :

some debugging in apt:

 - this is over https so there should be no proxy in the way
 - it is getting a 200 response for the gpg file with the correct size (316 bytes)
 - it's sending a conditional request for the Release file:

User-Agent: Debian APT-CURL/1.0 (0.8.16~exp5ubuntu6)
Host: private-ppa.launchpad.net
Accept: */*
If-Modified-Since: Sun, 28 Aug 2011 23:03:31 GMT
Cache-Control: max-age=0

... and getting a not-modified response.

deleting the 0-byte file from my cache gets things unjammed.

So, I'm not sure:
 * if, perhaps as part of bug 807303, Launchpad is ever disconnected before serving the files, things could be getting stuck here
 * conversely perhaps it's a bug in apt that it's caching a failed download, or not using a stronger cache validator

summary: - badsig error on update from private ppa
+ badsig error on update from private ppa due to 0-byte Release file
William Grant (wgrant) wrote :

archivepublisher doesn't write Release files atomically; there is a tiny window in each update where the file will be 0-length. That's probably what we've seen here.

Aaron Bentley (abentley) on 2011-08-29
Changed in launchpad:
status: New → Triaged
importance: Undecided → High
description: updated
tags: added: easy
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